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Discussion Starter · #1 ·
I just added a testpipe yesterday to my LS. I've got a 'replacement' muffler on it with dual 3.5 inch rolled tips at the end. I had the muffler shop make a y-pipe so I could use both tips (from the single outlet muffler).

Anyways, before the tp, the car sounded really nice and smooth all the way up to almost redline. It had a nice deep drone to it between 2 and 3k and growled when the vris plates opened up and the cai sucks in. Now though, it's got a metallic rattle noise from the rear of the car when I get on it. I can cruise around and keep the rpms down and it sounds beautiful-- almost a classic British car hum. So, I want to keep it on if I can resolve the rasping problem.

I peeked underneath the rear and noticed a few tiny places in the muffler and y-pipe seams that have had exhaust escaping.

Is the muffler just too weak to handle the extra 'flow' the testpipe makes? I understand that there's less backpressure now, but if I have to upgrade to a performance muffler, does that mean that I'll have even less backpressure--hence, louder rasping noise?

If anyone's had this problem, I'd appreciate some ideas/advice.

jeremy
 

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This is a common occurence when one replaces the catalyst with a straight piece of pipe.

The catalyst, on top of reducing emissions, also acts as a "buffer" & flow straightener which reduces turbulence in the exhaust. That rasping you're hearing is turbulence and without a device like a cat to straighten the airflow, there's not alot you can do.

You can try replacing the test pipe with a resonator or straight-thru style muffler (though I don't know how long the stuffing would last that close to the engine...) or you can try getting a high-flow cat from Catco or Random technology.
 

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Discussion Starter · #3 ·
how about replacing my resonator?

Thank you for the reply Mike. I wonder if it would help in softening the rattle if I installed a new resonator in place of the old one. This seems to be a popular 'fix' for a lot of people in here and on the ProbeTalk board. Can the resonator wear out (113k miles)? What exactly does it do?
 
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